Esters of acyloxycarboxylic acids



Patented Mar. 22, 1949 UNITED STATES TNT OFFICE ESTERS OFACYLOXYCARBOXYLIC ACIDS tary of Agriculture No Drawing. ApplicationOctober 10, 1946, Serial No. 702,349

4 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) This application is made under the act of March 3, 1883, asamended by the act of April 30, 1928, and the invention hereindescribed, if patented, may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment to us of any royalty thereon.

This application is a continuation in part of our copending applicationfor patent, Serial No. 567,294, filed December 8, 1944, patentedNovember 5, 1946, Patent No. 2,410,551.

Our invention relates to esters of alpha-acyL oxycarboxylic acids andmore particularly to compounds of the formula wherein R may represent asaturated aliphatic radical, particularly an alkyl radical such asmethyl, ethyl, propyl, butyl, heptyl, and nonyl, an aryl radical such asphenyl, a haloaliphatic radical such as haloalkyl like mono-, di-, andtrichloromethyl, dichlorobutyl, and so forth, a haloaryl radical such ashalophenyl like chlorophenyl, and an alkaryl radical such as alkylphenyllike tolyl and xylyl; R may represent a hydrogen atom or a methyl group;and B" may represent an alkenyl radical such as allyl, beta-methylallyl,crotyl, methyl vinyl carbinyl, and so forth, a haloalkenyl radical suchas beta-chloroallyl and gamma-chloroallyl, and an aralkenyl radical suchas cinnamyl.

This invention has among its objects the production of compounds thatare useful as solvents, plasticizers, insecticides, insect repellents,and chemical intermediates, Some of these compounds can be utilized asstarting materials in the production of derivatives which are substancespolymerizable into plastic, semi-solid or solid materials useful inindustry because of their tensile strength, elasticity, plasticity,resistance to water, organic liquids and gases, and because of otherdesirable properties. Other objects will be apparent from thedescription of the invention.

In general, the alpha-acyloxycarboxylic acid esters having theafore-mentioned general formula are obtained by reacting analpha-hydroxyacid, such as glycolic or lactic acid, with an oleflnicalcohol, and then reacting the oleflnic alphahydroxy acid ester thusobtained (e. g., glycolate or lactate), with an acylating agent to formthe olefinic alcohol ester of the corresponding acyloxy acid. Anothersuitable method involves reacting the acyloxy acid itself or thechloride or anhydride of the acyloxy acid, with the olefinic alcohol.

In preparing the compounds of the invention, the carboxyl group of thealpha-hydroxy or alpha-acyloxy carboxylic acid is esterified with anyaliphatic or aromatic primary or secondary olefinic alcohol containingan olefinic double bond and which may contain, in addition, halogensubstituents. Suitable alcohols include those in which the hydroxylgroup is linked to an alkenyl radical containing the grouping (ML 1 Isuch as allyl alcohol, beta-methylallyl alcohol, crotyl alcohol, methylvinyl carbinol, methyl propenyl carbinol, methyl isopropenyl carbinol,betagamma dimethyl allyl alcohol, gamma-gamma dimethyl allyl alcohol,beta-methyl gamma-isopropyl allyl alcohol; alcohols containing a,haloalkenyl radical such as beta-chloroallyl alcohol andgamma-chloroallyl alcohol; and alcohols having the hydroxyl group linkedto a phenylalkenyl radical, such as cinnamyl alcohol,

, Any saturated aliphatic or aromatic monocarboxylic acid free ofsubstituents other than halogen may be used as the acylating agent toesterify the alcoholic hydroxy group of the alpha-hydroxy carboxylicacid. Suitable acids are acetic, propionic, butyric, heptanoic,pelargonic, and other alkyl carboxylic acids; haloalkyl carboxylic acidssuch as mono-, di-, and tri-chloroacetic acids and betaandgamma-dichlorobutyric acids; phenyl carboxylic acids such as benzoicacid; halophenyl'carboxylic acids such as the various isomericmonochlorobenzoic acids and polychlorobenzoic acids; and alkylophenylcarboxylic acids such as toluic and Kylie acids.

In conducting the acylation of the olefinic esters of the alpha-hydroxyacids, we prefer to use as the acylating agent the anhydride or thechlo-- ride of the monocarboxylic acid, although the free acid or. anester thereof may also be used.

In the following examples, which are illustrative of the invention,Examples I to XII, inclusive, represent the preparation of some olefinicalphahydroxy acid esters, and Examples XIII to XXIV, inclusive, describethe acylation of these esters to form the compounds of the invention.

EXAMPLE I Preparation of allyl glycolate Allyl glycolate was prepared byinteracting glycolic acid with allyl alcohol and then distilling thereaction mixture to recover the ester. The procedure was similar to thatof Example III, the principal exception being the use of glycolic acidinstead of lactic acid.

EXAMPLE H Preparation of allyl lactate Two mols (180.2 g.) ofessentially 100 percent lactic acid, 2.2 mols (127.8 g.) of allylalcohol, 200 cc. of benzene, and 3 cc. of concentrated sulfuric acidwere refluxed for three hours while water was continuously removed, asformed, by use of a trap. Benzene and unreactecl allyl alcohol wereremoved by distillation under about 20mm. pressure, after which allyllactate Was distilled under 1 mm. pressure, its boiling point under thispressure being 27 to 29 C. The yield was 88 g., or 34 percent of thetheoretical. More of the ester, allyl lactate, was obtained by addingallyl alcohol, benzene and acid catalyst to the distillation residue,refluxing, and then distilling the reaction mixture as before.

EXAMPLE III Preparation of allyl lactate g. being obtained. Therecovered alcohol was returned to the reaction vessel containing thedistillation residue, 1 to 2 g, of p-to1uenesulfonic acid was added, andthe mixture again refluxed for several hours. Upon distillation, 159 g.of

allyl lactate was obtained. The total yield was thus 204 g., or 78percent of the theoretical. The residue (presumably polylactic acid)could doubtless be used again or added to a new batch of material, thuseventually converting virtually all of it into ester.

EXAMPLE IV Preparation of allyl lactate Ten mols (1125 g.) of 80 percentlactic acid, 400 ml. benzene, and ml. sulfuric acid were refluxed in astill having a 3-ft. column fitted with a water trap at its top, waterbeing drawn off, as it collected, at the rate of about 300 ml. in about5 hours. When production of water became slow, 40 mols (2323 g.) ofallyl alcohol were added, and refluxing continued with removal of about220 cc. of water, containing some allyl alcohol, in about 20 hours. Whenno. more water was produced, the flask was cooled, 20 g. of anhydroussodium acetate was added to neutralize the sulfuric acid, and thebenzene and about half the excess allyl alcohol were distilled atatmospheric pressure. The remainder of the alcohol was then distilledfairly rapidly under about 50 mm. pressure, after which the allyllactate was rapidly distilled at 60 C. and at 7 mm. The yield was 1178g., or 90.5 percent of the theoretical.

Allyl lactate is a clear, colorless, mobile liquid at room temperature,with a mild and not unpleasant odor. It boils at 60 C. under 7 min. ofmercury pressure, at 79 C. under 25 mm., and at 175.5 C. under 754 mm.pressure. It has a specific gravity of 1.0452 at 20 C., and a refractiveindex for the yellow sodium line at 20 C. of 1.4369.

EXAMPLE V Preparation of beta-methylallyl lactate Using essentially thesame procedure of Ex ample II, there was obtained from 3 mols (270 g.)of lactic acid and 3.3 mols (238 g.) of betamethylallyl alcohol, 143 g.of beta-methylallyl lactate, this being 33 percent of the theoreticalamount.

EXAMPLE VI Preparation of beta-methylallyl lactate Five mols (450 g.) oflactic acid and 5.5 mols (396 g.) of beta-methylallyl alcohol weretreated as in Example II, the yield of ester being 212 g. The recoveredalcohol was then returned to the reaction flask containing the lacticacid residue and refluxed for several hours. Distillation then gave g.of ester. A third period of reflux of alcohol and lactic acid residueyielded 39 g. of ester, a fourth yielded 34 g., and a fifth, 16.6 g.Addition of 50 cc. of fresh alcohol and 1 cc. of phosphoric acid raisedthe yield in the sixth period to 29 g. A further addition of 100 cc. ofalcohol gave a yield of 14 g. in the final reaction period, the totalyield being 460 g., or 64.6 percent of the theoretical. The product wascol lected at 77 to 79" C. under 11 mm. pressure.

EXAMPLE VII Preparation of beta-methylallyl lactate Aqueous sodiumlactate (84.5 g. of 64 percent by weight sodium lactate) and 67.8 g. ofbetamethylallyl chloride were heated in a rocking stainless steelautoclave at to C. for 5 hours. A moderate yield of beta-methylallyllactate was obtained by fractional distillation of the reaction mixture.

EXAMPLE VIII Preparation of beta-methylallyl lactate Beta-methylallyllactate was obtained by interaction of methyl or ethyl lactate with betamethylallyl alcohol. In this case 3 mols of methyl lactate, 6 mols ofbeta-methylallyl alcohol, and 10 g. of aluminum tert.-butoxide weremixed and refluxed in a still from with methanol was withdrawn as fastas it collected at the still-head. When production of methanol ceased,betamethylallyl lactate was recovered from the reaction mixture byfractionation under reduced pressure. The yield was 70 percent of thetheoretical.

Beta-methylallyl lactate is a clear, colorless, mobile liquid at roomtemperature with a mild odor. It has a boiling point of 69 C. under 8mm. of pressure and a boiling point of 78 C. under 11 mm. It has aspecific gravity of 1.0181 at 20 C. and a refractive index for theyellow sodium line at 20 C. of 1.4380.

EXAMPLE IX Preparation of beta-chloroallyl lactate Ten mols (1125 g.) of80 percent lactic acid,

400 ml. benzene, and 5 ml. of sulfuric acid were refluxed in a stillhaving a 3-ft. column fitted with a water trap at its top, water beingdrawn off, as it collected, at the rate of about 300 ml. in about 5hours. When production of water became slow, 4.0 mols (3700 g.) ofbeta-chloroallyl alcohol were added and refluxing continued with removalof about 220 cc. of water in about 20 hours. When no more water wasproduced, the flask was cooled, 20 g. of anhydrous sodium acetate wasadded to neutralize the sulfuric acid, and the benzene and about halfthe excess beta-chloroallyl alcohol were distilled at atmosphericpressure. The remainder of the alcohol was then distilled fairly rapidlyunder 50 mm. pressure, after which the beta-chloroallyl lactate wasdistilled at about 83 C. and at 5 mm. pressure. The yield was 76 percentof the theoretical.

EXAMPLE X Preparation of gamma-chloroallyl lactate Gamma-chloroallyllactate was prepared by the alcoholysis of methyl or ethyl lactate. Inthis case 3 mols (312 g.) of methyl lactate, 6 mols (555 g.) ofamma-chloroallyl alcohol, and 10 g. of aluminum tert.-butoxide weremixed and refluxed in a still from which methanol was withdrawn as fastas it collected at the stillhead. When production of methanol ceased,the excess alcohol was distilled at 54 C. and at 13 mm., after which theproduct, gamma-chloroallyl lactate, was obtained at 105 C. and at 12 mm.The yield was 65 percent of the theoretical.

EXAMPLE XI Preparation of methyl vinyl carbinyl lactate The procedure ofExample IX was slightly modified to prepare methyl vinyl carbinyllactate since methyl vinyl carbinol is somewhat unstable in the presenceof sulphuric acid. In this case, the lacti-ce acid, alcohol and benzenewere mixed and refluxed with removal of water until little water wasproduced. Then 10 g. of p-toluenesulfonic acid was added and heatingcontinued. When no more water was produced the catalyst was neutralizedand the product distilled as described in Example IX.

EXAMPLE XII Preparation of crotyl lactate The same procedure as inExample XI was followed to prepare crotyl lactate, since crotyl alcoholis also unstable in the presence of sulfuric acid.

EXAMPLE XIII Preparation of allyl aZpha-propzonomyacetate One gram ofsulfuric acid was dissolved in 1 mol (116 g.) of allyl glycolate in aflask fitted with stirrer, dropping funnel and reflux condenser, and 1.1mols (143 g.) of propionic anhydride was slowly added with agitation andwhile maintaining the reaction mixture at about 60 to 80 C. The contentsof the flask were then heated at 100 C. for 2 hours, allowed to standovernight at 25 C., and then distilled under reduced pressure. Allylalpha-propionoxyacetate was collected at about 63 C. under 1.2 mm.

EXAMPLE XIV Preparation of allyl aZpha-acetomypropionate To 1.5 mols(195 g.) of allyl lactate there was slowly added, with stirring, 1.65mols (168 g.),

10 percent excess, of acetic anhydride. The mixture was warmed to 50 to60 C. to start the reaction, after which cooling was used to keep thetemperature below 100 to 110 C. After standing an hour, the mixture wasfractionated under a pressure of 7 mm., the product being collected atto 81 C. The yield was 230 g., or 89 percent of the theoretical.

Allyl alpha-acetoxypropionate is a clear, colorless, mobile liquid ofslight, though pleasant odor. It has a boiling point of 81 C. under 7mm. pressure, a specific gravity of 1.0544 at 20 C., and a refractiveindex for the yellow sodium line at 20 C. of 1.4270.

EXAMPLE XV Preparation of beta-methylallyl alpha-acetoacypropz'onateUsing essentially the procedure described in Example XIV, except that 1to 2 cc. phosphoric acid was used as a catalyst and the temperature wasmaintained at 60 to 80 0., there was ob tained from 1.5 mols ofbeta-methylallyl lactate and 1.8 mols of acetic anhydride a yield of 260g. of beta-methylallyl alpha-acetoxypropionate, this being 93 percent ofthe theoretical yield.

The product was collected at 100 to 102 C. at

12 mm. pressure.

Betanethylallyl alpha-acetoxypropionate is a clear, colorless, mobileliquid with a slight, though pleasant odor. It has boiling points of 76C. under 3 mm., 87 C. under 5 mm., and C. under 10 mm. pressure. It hasa specific gravity of 1.0330 at 20 C., and a refractive index for theyellow sodium line at 20 C. of 1.4314.

EXAMPLE XVI Preparation of beta-chloroallyl alpha-acetoxypropz'onateBeta-chloroallyl alpha-acetoxypropionate was prepared by interactingbeta-chloroallyl lactate with acetic anhydride and then distilling torecover the ester, the procedure being essentially that used in ExampleXIV.

EXAMPLE XVII Preparation of gamma-chloroallyl alpha-acetoxypropionateUsing the procedure of Example XIV, gammachloroallylalpha-acetoxypropionate was prepared by reacting gamma-chloroallyllactate and acetic anhydride.

EXAMPLE XVIII Preparation of methyl vinyl carbinylalphaacetomypropionate Methyl vinyl carbinyl alpha-acetoxypropionate wasprepared by reacting methyl vinyl carbinyl lactate with aceticanhydride, using essentially the same procedure as in Example XX.

EXAMPLE XIX Preparation of crotyl alpha-acetozrypropz'onate stirrer,dropping funnel and reflux condenser, and 1.1 mols (174 g.) of butyricanhydride was slowly added with agitation and while maintaining thereaction mixture at about 60 to 80 C. The contents of the flask werethen heated at 100 C. for 2 hours, allowed to stand overnight at 25 C.,and distilled under reduced pressure. Allyl alpha-butyroxypropionate wascollected at about 59 C. under 0.5 mm. The yield was 178 grams.

EXAMPLE XXI Preparation of beta-methylallyl alpha-promonoxypropionateUsing the same general procedure as in Example beta-methylallylalpha-propionoxypropionate was prepared by reacting beta-methylallyllactate with propionic anhydride.

EXAMPLE XXII Preparation of allyl alpha-pelargonozcypropionate EXAMPLEXXIII Preparation of beta-chloroallyl alpha-hemogloarypropionateBeta-chloroallyl alpha-heptoyloxypropionate was prepared by reactingbeta-chloroallyl lactate with heptanoic acid chloride in the presence ofpyridine, using essentially the same procedure as in Example XXII.

EXAMPLE XXIV Preparation of allyl alpha-benzoyloxypropionate Using theprocedure described in Example XXII, allyl alpha-benzoyloxypropionatewas prepared by reacting allyl lactate with benzoyl chloride in thepresence of pyridine.

The following table illustrates the properties of some of thesecompounds:

Ester 5 33 N a.

Allyl glycolate 72 B 1. 4418 l. 0901 Beta-chloroallyl locate 83 5 1.4627 1. 2153 Gamma-chloroallyl lactate 106 12 l. 4670 1. 2166 Crotyllactate 92 18 1.4420 1. 0106 Methyl vinyl carbinyl lactate.. 58 8 1.4326 1. 0091 Beta-chloroallyl alpha-acetoxypropionate 96 5 1. 4460 1.1792 Crotyl alpha-acetoxypropionate..- 94 8 1. 4347 1. 0338 Methyl vinylcarbinyl alphaacetoxypropionate 8 1. 4256 1. 0233 Allylalpha-butyroxypropionate.. 59 0. 5 1. 4304 l. 0110 Ally]alpha-propionoxyacetete 63 l. 2 1. 1321 1. 0068 Beta-methylallylalpha-propionoxypropionate 3. 5 1.4324 1.0117 Allyl alpha-pelargonoxyproonate 102 0. 2 1. 4400 0. 9568 Beta-chloroallylalpha-heptoyloxypropionate 107 0.4 1. 4480 1. 0544 Allylalpha-benzoyloxypropionate 108 0.1 1.5042 1.1113

CHESSIE E. REHBERG. CHARLES H. FISHER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,183,357 Ritchie Dec. 12, 19392,367,798 Rehberg et al. I Jan. 23, 1945 2,388,440 Rehberg et a1. IINov. 6, 1945 2,410,551 Rehberg III Nov. 5, 1946 OTHER REFERENCES Joneset al., Jour. Chem. Soc. (London,

Fisher et al., Jour. Am. Chem. 300., vol. 65 (1943), pp. 763-767.

